Purpose: To assess the accuracy of the Tonosafe disposable prism tonometer head via a randomised controlled prospective trial.
Methods: The intraocular pressure (IOP) of 69 patients (31 men, 38 women) involving 137 eyes was measured using both the Tonosafe disposable and the Goldmann tono-meter head. The average age of patients was 66.5 years (range 23-93 years). The two examiners (PM and SL) who performed tonometry were masked while a separate observer read the IOP measurements. The order was randomised between Tonosafe and Goldmann devices. The minimum interval between the two measurements was 15 min. Patients with corneal and external diseases were excluded from the study.
Results: The mean IOP using the Goldmann tonometer head was 17.44 +/- 4.97 mmHg. The mean IOP using the Tonosafe disposable head was 17.58 +/- 5.03 mmHg. The mean difference was 0.14 +/- 1.73 mmHg (95% CI -0.44, 0.16, P= 0.36). Subgroup analysis on eyes with IOP > 21 mmHg showed the Tonosafe disposable head was on average 0.15 +/- 2.40 mmHg higher than the Goldmann tonometer head. There was a high level of correlation between the IOPs obtained with the Goldmann and Tonosafe heads. Pearson's coefficient of correlation was 0.94 (P < 0.0001).
Conclusion: The Tonosafe disposable prism head was found to be accurate in IOP measurement, even in the higher range.